Concrete preparation for the foundation: building codes and rules for footing

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Date: October 27, 2018

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When carrying out construction, it is important to correctly perform preliminary calculations, as well as technically competent and high-quality preparation of the foundation, which determines the stability of the building’s foundation. Concrete preparation for the foundation is a complex of works for the construction of a cushion under a future facility.

The choice of the optimal option for performing preparatory measures affects the reliability of the foundation and the service life of the construction project.

A properly prepared base, proportional to the area, redistributes the loads acting on the ground and prevents leakage of the cement mass, which is possible during the process of pouring concrete mortar.

Forming a pillow is a responsible operation. That is why the technical requirements that determine the specifics of preparatory activities, the technology, the required material, and the thickness of the layer used for the pillow are regulated by SNiP and a set of rules, the recommendations of which we will consider further in more detail.

There are a number of technical requirements regulating the technology of preparatory work, the choice of material and the thickness of the layer used for the pillow

Preparing the foundation pit

The main stages of work to prepare the soil for installing a concrete foundation include:

• arrangement and marking of the pit, taking into account the future thickness of the layer of sand-gravel mixture and concrete;

planning and cleaning the bottom of the excavation;

• compaction of loose soil using vibrating plates;

Regardless of the type of soil, at the first stage of work on preparing lean concrete for the foundation, the bottom of the excavation should be leveled

• additional moistening or drying of the soil, depending on the results of compaction work;
• adding sand-crushed stone fraction 10 cm thick, necessary for drainage;
• compaction of the massif;
• applying a waterproofing layer of film or roofing material sheets;
• assembly of formwork with a height of no more than 30 cm for concreting.

Only after this they begin concreting work. These are the main stages provided for by the standards that make up the concrete preparation for the foundation.

The right vertical layout solution

The safety and quality of building a house is impossible if the hydrological conditions of the area where construction is taking place are not taken into account. For example, if the house is built in a lowland, it is necessary to provide for the possibility of frequent flooding. If the hydrological conditions of the area are far from perfect, it is advisable to build the house on an embankment. Utility rooms must be placed so that groundwater in any case remains at least 50 cm below the base of the foundation. If a garage is being built, the entrance ramp is built with a slope away from the building.

Alas, it is not always possible to build houses under favorable conditions. If construction is planned in a lowland, it is necessary to provide the correct solution for the vertical layout of the building site and design the drainage of atmospheric waters. When planning saunas, storerooms, and garages located underground, a drainage system will be required, otherwise the premises will quickly become unusable.

A reliable drainage system is unthinkable without the presence of a storm sewer near the construction site. Thus, the construction of a recessed garage involves a deep pit with a ramp. To drain rainwater that will flow down the ramp, you need to build receiving grates through which the water will flow into the storm drain. And all this must be done before work on the construction of the foundation begins.

The issue of rainwater drainage is very important. If the house is built and there is no storm sewer, large water intakes will have to be made, and this is very labor-intensive. Another option is to create open ditches that will be discharged into low areas. This may simply not be feasible, since ditches will have to be laid through the neighbors’ properties.

Building your own home is not an easy task, and it’s not for lack of significant savings. This is an objective reason.

Many people are stopped by the fact that they do not know where to start building a house on their site. The variety of types of work, costs, documents, time, the risk of making a mistake and its possible consequences are scary. Our goal is to provide information on how to step by step complete all stages of building a private house with your own hands. And the final decision is yours.

Where to start building a house on your site

Performing reinforcement

According to building codes, concrete preparation for the foundation requires strengthening the concrete mass with steel reinforcement. This measure improves the reliability of the part of the building located below the zero level and strengthens the footing.

The base is reinforced with steel mesh connected with special wire with a diameter of 8 millimeters. The structure is laid on the base before the formwork is filled with the mixture. The standards provide for the installation of vertically located steel rods that ensure a strong connection between the foundation and the base. Steel rods must rise above the surface of the base by at least 20 centimeters.

Reinforcement significantly strengthens the concrete base and increases the reliability of the underground part of the structure

Regulatory documents - SNiP and Code of Rules (SP)

The construction of any structures during the construction of civil and industrial facilities is subject to certain requirements specified in the relevant SNiP and other standards of state and industry significance. Concrete preparation for the foundation is carried out based on:

These documents define measures for the design and installation of foundations, taking into account:

• soil type;
• surrounding buildings;
• effective loads;
• seismicity;
• environmental requirements.

The thickness and width of concrete preparation for the foundation is calculated, according to SNiP, based on bearing capacity and possible deformations. In the first case, calculation is required if:

• significant compressive loads are expected;
• the structure is supposed to be located near slopes, on a slope or embankment;
• There are weak soils under the base of the foundation.

It should be noted that SNiP allows not to carry out calculations of bearing capacity if the project provides for measures that exclude soil displacement for the previously mentioned reasons.

All long-term and short-term forces transmitted from the structure, including the weight of the underground part of the structure, are taken as loads on the concrete preparation of the foundation. Possible combinations are indicated in SNiP.

Features of concrete preparation

The main provisions contained in building codes and codes of practice related to the implementation of a cushion based on lean concrete:

• It is allowed to use a solution of grade M50 and higher. To perform the work, lean concrete is used, which is a type of cement mortar that contains no more than 6% class B15 cement. Sand and gravel play the role of filler.
• The poured mass for foundation slabs or a monolithic base must extend beyond the level of the underground part of the structure and rise above it by 100-150 mm, which is ensured by the design of the formwork prepared in advance.
• The solution is poured onto a pre-made crushed stone-sand base.
• Air bubbles are removed by compacting the mixture.
• Protection against surface dehydration is provided by polyethylene film, which is used to cover the poured surface in the first days.

Is it possible to make a footing without reinforcement? What is the recommended thickness of the concrete footing made without reinforcement by building codes? Building rules allow this option, for which the thickness of the concrete layer is 150-200 mm.

When arranging a reinforced base for a foundation, the set of rules allows for a reduced base height. The layer thickness in this case is 60-100 mm. The size is influenced by the mass of the structure, the level of groundwater, and the type of soil.

Construction requirements provide for a minimum height of the concrete layer, which must rise above the ground surface by no less than 15 cm

According to SNiP, the tolerance for surface flatness when forming a monolithic strip does not exceed 0.5 cm for each meter of length and no more than 5 centimeters for solid slabs with a width of over 25 meters.

Concrete preparation for the foundation is especially important if construction activities are carried out in winter, since a flat surface facilitates the further implementation of the foundation work envisaged by the project.

Concreting the slab and maintaining the concrete

The formwork is in place, the reinforcement cage is installed. All that remains is to lay concrete in the floor slab.

The contour of the future slab should extend onto the walls by at least 7 cm if the wall material is concrete blocks or brick. And at least 15 cm for blocks made of slag concrete or aerated concrete.

We make the concrete mixture directly on site. It’s better, of course, to bring it ready-made and feed it into the structure with a concrete pump, but this will cost much more.

We will install the concrete mixer as close to the installation site as possible.

We place the concrete mixture into the structure and compact it with a vibrator

We mix the concrete, pour it into the structure, distributing it and thoroughly compacting it with a vibrator. Smooth the surface. To keep the slab level, we use the rule. To obtain a slab of the required thickness, we focus on pre-tensioned threads.

Important

! The entire volume of the slab must be filled at one time. Breaks in concreting are unacceptable. Perhaps for a short rest, while the concrete mixer “spins” the next portion of the mixture. I recommend: Installing beacons for plastering walls with your own hands

It is impossible to use beacons made of galvanized steel, which remain in the concrete body when installing the floor slab.

We fill the slab not in separate sections, but continuously, moving from one edge of the slab to the other. Cover the poured slab with plastic wrap.

Performing crushed stone preparation

The use of prepared foundations based on crushed stone allows you to reduce the costs of construction activities. After all, cement is saved, and the cost of purchasing crushed stone is quite acceptable. Crushed stone preparation for the foundation is permitted by the set of rules and building codes. In this case, the layer thickness should be about 20 centimeters. The crushed stone layer must be thoroughly compacted and filled with liquid bitumen. Filling the bitumen solution is carried out if it is necessary to saturate the soil as much as possible or to form a waterproofing bitumen film.

This method does not provide high rigidity of the substrate and makes it difficult to carry out foundation measures. It is widely used for low-impact construction of technical facilities, utility rooms and auxiliary buildings.

Concrete preparation for the foundation

Before work on the construction of the foundation structure begins, load-bearing preparations are made. This technical documentation contains regulatory requirements for work technology, materials used and layer thickness depending on the type of soil and some other conditions. The procedure and rules for its construction are regulated by SNiP 52-101-200, and also partially in:

Concrete preparation is a bulk compacted cushion on which the foundation of a building or road surface materials rests. The stability of the foundation structure, and therefore the durability of the entire building as a whole, largely depends on the quality of this stage of work.

The support cushion device can be made of well-compacted crushed stone or lean concrete.

Despite the fairly long period of use of this technology in construction, disputes often arise as to whether or not it is worth installing such a pillow or whether this stage can be skipped. The video below provides arguments in favor of both opinions and provides conclusions from reputable experts in this field.

Regulations

The arrangement of the foundation cushion is approached with the same responsibility as the other stages of construction and installation work. The process under consideration is described in SNiP 52-01-2003 “Concrete and reinforced concrete structures”, as well as SP 50-101-2004 and SP 52-101-2003. The documents outline the main points of the work:

• type of crushed stone, layer thickness;
• the grade of concrete used is not lower than M50, it is optimal to use M50 or M100 depending on the size of the cushion;
• the procedure for calculating the thickness of the concrete base and the substrate itself is given, depending on the type of soil and the mass of the building;
• size of reinforcement for the frame, type of rods, need for them. Yes, it turns out that the pillow can be reinforced!

Crushed stone pillow

The construction project must necessarily contain data on the method of concrete preparation, the materials used for this and the thickness of the layers. On stable soils and groundwater below the freezing point, the thickness of the crushed stone layer is usually 200 mm. In this case, crushed stone is poured into the bottom of the trench when installing a strip foundation or over the entire building area when installing slab structures and is well compacted. The quality of compaction of the layer ensures the stability of the foundation structure and the absence of subsidence in the future.

At the same time, it is important to choose the right crushed stone; its strength should not be lower than M1200.

After excavating the soil to the required depth, the bottom of the trench or pit is compacted and covered with a membrane fabric such as geotextile. This prevents the germination of weeds and reduces the likelihood of moisture penetration into building structures. When constructing slab-type foundations, a layer of crushed stone is covered with rolled waterproofing, on top of which heat-insulating slabs are laid.

Compacting gravel with a vibrating machine

Crushed stone preparation for the foundation is not only a good support cushion, but also an effective drainage layer that drains water coming from the surface into the ground. The presence of a profile geotextile membrane allows the movement of moisture in only one direction.

Participants share their experience in building stone fences: from simple to the most complex.

It’s not for nothing that a fence made of corrugated sheets won the title of “national” - today this type of fencing can be found everywhere. But stone fences, although more expensive and complex in construction, are not losing their positions. Many developers dream of just such a fence and consider it both more reliable and more worthy, especially for the “front” part of the territory.

In this article we will consider the following questions:

• What nuances should you be aware of before starting construction of a stone fence?
• What foundation to choose for a stone fence.
• What construction “tricks” will allow you to save money?
• How can you decorate a stone fence?

Application of lean concrete

The use of concrete mixture for foundation preparation is a more expensive technology than the use of crushed stone. In this case, the base material is a mixture of 5-6% cement with a strength class of up to B15 and fillers in the form of sand, gravel or crushed stone. In this case, there should be 3-4 times more stone materials. You can read more about this solution here.
As for the exact composition of lean concrete, it is as follows:

• 2200 kg of sand;
• 160 kg of cement;
• About 75 liters of water.

The thickness of the concrete layer depends on the type of soil, the weight load of the building, the groundwater level, the depth of freezing and can be in the range of 50-100 mm. Before pouring concrete, a membrane is laid in the foundation trench or pit and a layer of crushed stone or a sand-crushed stone mixture 100-400 mm thick is filled. After compaction, the bulk cushion is covered with another membrane layer so that when pouring concrete, the cement mortar does not go down.

Expanded clay can be used as a filler for preparing concrete. However, in this case the amount of cement must be doubled. This mixture has certain heat-insulating properties, but is more expensive and more difficult to prepare.

Using a profile membrane

One of the main tasks of such preparation is to prevent premature drying of the concrete solution, including the seepage of water into the ground. To solve this problem, a type of insulation such as a profile membrane is sold on the modern market. Speed ​​of installation and low price are the main advantages of this material. However, many builders doubt its reliability.

Concrete preparation for slab foundations

The supporting base for the monolithic foundation slab is laid over the entire building area. Under the concrete you need to pour a crushed stone-sand mixture, which you can make yourself or buy ready-made. The underlying layer of sand and crushed stone must be leveled, compacted well and covered with a membrane sheet, but which will be poured with lean concrete.

On dense, stable soils, it is allowed to use a dry cement-sand mixture without crushed stone for foundation preparation. To do this, add 700 kg of sand to each bag of cement (50 kg) and mix well. After this, the mixture is poured into a pit, leveled in a horizontal plane and watered with water through a sprayer. To ensure the necessary moisture during setting, it is recommended to cover the material with film.

Preparation for a monolithic strip foundation, 5 stages

After marking has been completed in accordance with the project and soil has been excavated to the required depth under all walls, the foundation preparation work begins:

• the bottom of the trench is leveled and compacted using a tamper;
• pour a crushed stone layer 50-100 mm thick, compact it and cover it with a layer of geotectile;
• install formwork from boards 150-200 mm wide, with stops installed on the walls of the trench;
• to increase strength, a steel reinforcing mesh of 6-8 mm wire with a mesh size of no more than 150 mm is laid along the entire length;
• pour lean concrete to the top level of the formwork and compact it using a vibrating plate.

Laying geotextile fabric will prevent the cement mortar from flowing downwards from the concrete mixture and will ensure the quality of foundation preparation. It is possible to replace the canvas by pouring a layer of hot bitumen, but such a layer will be more expensive. The reinforcing mesh should be raised above the canvas by 5 cm, resting on stones or special plastic supports. The distance from the outer wire to the formwork wall must be at least 25 mm.

To ensure reliable connection between the concrete pad and the monolithic foundation, it is recommended to insert reinforcing pins into the concrete. They should protrude upward by 25-30 cm. It is better to make the width of the preparation tape 10-15 cm wider than the foundation monolith; you can read more about reinforcement on this page .

Brand of concrete for covering a private house

Strong and reliable concrete floor slabs can only be obtained with strict adherence to technology, correct mixing and proper selection of the ratio of concrete mortar components.

Mixture composition

The composition of any concrete solution includes the following components: cement, crushed stone or gravel, sand, water. The mixture is prepared in a concrete mixer, which ensures a higher quality of mixing and, accordingly, the final solution than with the manual method.

The main component of a concrete mixture is cement, the consumption of which depends on the brand of the finished mixture. Sand is chosen from river sand or any sand (but pre-cleaned from clay, which can make the sand greasy and unsuitable for work). Crushed stone is chosen in fractions of 10-20 millimeters; it must be clean, without screenings and debris. Add clean water, without any impurities, so that the solution does not separate.

Prefabricated strip foundation

The construction of this type of foundation is carried out from concrete or stone blocks made in the factory or independently. At individual development sites, blocks of various types of foam concrete are often used for this purpose. The reduced weight of such building structures allows the use of a compacted bedding made of sand and crushed stone as a support cushion. Concrete preparation is used only for large, heavy buildings. The technology for performing the work is similar to the preparation device for monolithic structures.

Scheme of the device on a sand bed

The thickness of the preparation layers depends on the type of soil and the total weight load of the house. For dense types of soil, a thickness of 100-150 mm is sufficient. For softer or moist soil, the concrete layer must be increased. A cushion of sand and crushed stone of at least 15 cm. To compact it, you can use a hand tamper or spill it with water.

Diagram of the device on a crushed stone cushion

The preparation device for a prefabricated strip foundation allows for stage-by-stage execution of work with interruptions, which is impossible when installing reinforced concrete monolithic structures.

What to remember when laying the foundation

When building the foundation, we must not forget about communications. All necessary preparations for pipelines and cables must be made in advance. You will need to leave holes for communications.

Finishing the foundation of a house with stone is done after the base has set well. It can also be used for landscaping the local area. Installation of stone is done by hand.

Often the owner of the house cladding not only the base, but also the walls. If you hire a construction team for such work, the costs will increase exponentially.

A foundation without reinforcement is unstable to seismic influences. If it is used to build a one-story house, then there is no guarantee that cracks will not form in the walls.

Support pad for a columnar foundation

To erect support pillars, a trench is dug 40-50 cm wider than their cross-section and 20-30 cm deeper than the design value of the backfill.
After this, formwork is installed at the bottom of the trench in the places where the supports are erected. Its dimensions should exceed the cross-section of the pillars by 5-10 cm on each side. A 10-15 cm layer of crushed stone is poured inside the formwork, compacted well and covered with an insulating membrane. After this, a reinforcing mesh of rod or wire with a diameter of 6-8 mm is laid, lean concrete containing 5-6% cement is prepared and poured into the formwork. Laying out pillars can only be done after the concrete has reached 80% strength. This usually happens within 4-5 days.

The cost of foundation concrete preparation in the estimate

The use of technology using lean concrete when constructing a supporting foundation pad leads to higher construction costs. Therefore, its use must be justified by calculation, and the design of the layers and the materials used must be precisely indicated in the project.

The increased reliability of such a design can be justified when constructing heavy stone buildings with a height of more than one floor. In addition, the concrete pad is used on weak, swampy and heaving soils.

The cost of performing work on foundation preparation using lean concrete depends on the volume of material and averages 1100-1400 rubles/m 3 . The larger the total volume, the cheaper the builder charges for their work.

Concrete is a stone building material obtained by hardening a semi-liquid mixture poured into a mold and compacted. It is prepared by stirring.

Foundation structures are exposed to moisture coming from seasonal increases in groundwater, when snow melts and after heavy rains. Wherein .

The technology for performing monolithic work is a method of constructing elements of buildings and structures from concrete mixture and reinforcement using special formwork.

The technology of constructing monolithic walls during the construction of buildings, structures and structures belongs to the category of the most common methods of modern construction. This is due.

Buy a ready-made house project

Be sure to select and buy a ready-made house project.
The house design is selected based on certain requirements - find out here.

Before purchasing a project, show it to a specialist (architect, builder with experience), listen to his opinion about the project. If possible, try to visit a house that was built according to the chosen project.

Pay attention to the technologies used in the construction of a house according to the chosen project. Is the construction technology suitable for you and how does it fit in with the planned method of building the house?

Are you going to carry out the work yourself or will you use the services of private teams or a reputable construction company for turnkey construction.

Products for construction and repair

⇆

Make sure that the purchased project is sufficiently detailed, then during construction there will be no additional difficulties.

When purchasing, check the climatic conditions for which the project was made - outside air temperature, snow and wind loads.

Linking a house project

Instruct local designers to adapt (adjust) the project to the conditions of the construction site.

Be sure to tie the foundations

to the ground conditions of the construction site. Compliance of the foundation with the soil conditions and the structure of the house will ensure the necessary minimum costs for its construction.

Major changes in the project: replacing the material and arrangement of walls, the size of openings in the walls, installing additional windows, replacing floors, must also be entrusted to specialist designers.

Be sure to think about what engineering systems your home will be equipped with.

In addition to the traditional and mandatory engineering systems - electricity, heating, water supply, sewerage, ventilation, decide on the need to have in the house and on the site:

• Air conditioning system.
• Professional air humidification system.
• Security and fire alarms.
• Protection against flammable gas leaks and indoor gas contamination.
• Intercom.
• Video surveillance system.
• Devices for receiving television and Internet signals.
• Central vacuum cleaner.
• External lighting of the site and access to the site.
• Plumbing on site.
• Backup electric generator.
• Control system for entrance gates to the site.
• Protecting your home from lightning strikes.
• Separate elements of the Smart Home system. For example, control of climate control systems of heating, air conditioning and humidification in order to regulate temperature and humidity in rooms depending on the weather and the presence of people.

The design of the systems must be provided for in the house design. Often the solution to this issue is left for later, and this inevitably leads to alterations; it is necessary to adapt options that are not the most effective, convenient and cheap.

Make all changes to the project before construction begins.

This will allow you to avoid rash decisions and additional costs during the construction process.

The designer will develop a drawing - a plan for the location of the house and other structures on the site, taking into account your wishes, the requirements of the village administration and SNiP.

On the site plan it is necessary to select in advance and indicate on the drawing

the location of not only the house, but also the septic tank, treatment facilities, well or well, outbuildings, driveways, paths and areas for recreation and parking, as well as the route of water supply pipes, sewerage and ground heat exchanger, the place where electrical wires enter the house.

A drawing with a site development plan will be required to obtain permission to build a house.

At the design stage, if there are already neighbors’ houses nearby, try to find out their experience:

• what kind of sewage system they have and where;
• who has what foundation;
• what is better, a well or a well, how deep and where they are located;
• what is the level of groundwater in the area in spring and autumn;
• what soils lie and at what depth.

This information will help you, together with the designer, choose the optimal solutions for the location and design of water supply and sewerage systems, as well as the design of the foundation of the future home.

Why do you need a concrete footing - 2 types of preparation for the foundation

Before starting the installation of the foundation of a house or other structure, a set of preparatory measures is carried out. Concrete preparation for the foundation is an important step in creating a stable and durable load-bearing structure. An element of the structure, such as a layer of monolithic mortar, covers the foundation pit and serves as a shock absorber and load distributor.

What is a concrete footing and why is it needed?

Definition and purpose

Concrete preparation for the foundation is the work of pouring a layer of monolithic material, which will ensure economical and convenient construction of the main load-bearing structure. The primary task of installing a concrete footing is to strengthen and level the site for further concreting. As an option, you can make a pillow from a roll product, sand, crushed stone, or a combined type of structure from two materials. But the properties of these products do not allow creating a stable structure on weak types of soil - peat, sapropel, waterlogged clay.

Regulatory documents required for the installation of concrete footings: SNiP 52-01-2003, SP 50-101-2004. The thickness of the concrete preparation is about 100 mm. Its main purpose is to create reliable support for the foundation of a building under unfavorable environmental factors and operational features of the building, for example:

The layer of this base should not be very thick.

• On weak and mobile soil.
• In areas with elements of complex natural and artificial relief (slopes, embankments, slopes).
• With high compressive loads from the building.
• In regions with increased seismic activity.

When constructing objects in winter, constructing a base made of lean concrete simplifies the installation of the load-bearing base of the structure.

Functions of the structure

Concrete preparation performs a number of secondary, but no less important tasks:

• Creation of a hydrobarrier. When pouring concrete for the foundation, the liquid mixture will not seep into the ground, while moisture is retained in the mortar mass.
• Formation of a flat surface. Under such conditions, the consumption of concrete mixture is reduced.
• Protection from surface moisture. The foundation is vulnerable to groundwater; the protective layer increases its resistance to an aggressive environment.
• Redistribution of loads. The concrete pad takes on the entire weight of the structure and smoothly distributes it onto the ground.
• Creation of improved conditions for installation of reinforced frames. It is easier to lay the skeleton elements on a finished concrete pad.
• Resistance to shrinkage processes. The structure is reliably kept afloat and is not destroyed by ground movement.
• Increase in strength and performance indicators. The shock-absorbing cushion improves the properties of the structure.

About the types

There are quite a few types of natural stones that are used in construction and decoration. The most popular types are:

1. Granite. It has excellent strength indicators. At the same time, it weighs quite a lot. Granite is sold in different forms. These are slabs, paving stones, and boulders. This material is excellent for creating garden paths and platforms, and for decorating a patio. It is also used for interior work.
2. Another durable stone is quartzite. It differs from granite in its very beautiful and pronounced texture. It shimmers very beautifully under the sun's rays.
3. Dolomite is of crystalline origin. Its structure is layered and homogeneous. At the same time, it is very durable. The beauty of this stone is unique.
4. Many people know and have heard about marble. It is considered a very elegant material, but is very expensive. Marble comes in different colors and shapes. Its surface is ground and polished to perfection. The material is excellent for finishing swimming pools, fireplaces, bathrooms and so on.
5. A stone such as slate is not durable, but it is easier to process. It has a layered structure, thanks to which you can create unique textures. Slate is not suitable for paving paths and areas. It is best used for wall cladding.
6. Limestone is also easy to work with. It varies in strength. Durable limestone is used in construction. However, due to its porous structure, this material is considered fragile. Therefore, it is more often used for cladding. Limestone strongly absorbs water, so it requires the use of water repellents.
7. Sandstone is also inferior in strength to granite and marble. It is easy to process and is quite inexpensive. Sandstone is often used to decorate barbecues, paths, platforms, ponds, and so on.
8. As for pebbles, they are distinguished by their rounded shapes and pleasant-to-touch surface. This stone is very dense and durable. It is used for paving paths and creating artificial reservoirs.
9. If we talk about shell rock, it is very often used in the construction industry. The structure of the stone is porous, and it consists of crushed sea shells.
10. Another type of natural stone is travertine. It is stronger than marble. As for frost resistance parameters, travertine has higher parameters than limestone and dolomite.
11. The most common rock is basalt. This is a stone of igneous origin. Basalt has a predominantly dense structure. However, basalt can also be porous. The color of the stone is always dark.
12. A stone such as tuff is a combination of products from volcanic eruptions and mud flows that have been cemented by sand, ash, glass, and so on. It is worth noting that tuff can also be calcareous. This material is formed from deposits of carbonated lime in springs.
13. Jasper consists of opaque crystalline quartz, which turns different colors when exposed to iron oxides. Jasper is widely used to decorate a wide variety of objects.

Varieties

Sand pillow

The construction of a foundation on such material optimally distributes the impact of the soil. This version of the concrete footing is constructed in mid-spring or autumn, when the soil stops seasonal movement. When using this type of preparation, the bottom of the load-bearing base rises above the level of soil water, so the concrete structure avoids the destructive influence of ground moisture. This type of foundation cushion is used on soils with high humidity. The thickness of the layer is set within 15 cm.

To make a sand substrate you need a material with the following characteristics:

• Fraction 2-2.5 mm. The most suitable sand is low density, capable of good moisture permeability.
• Clay particles, limestone, salt deposits. Minor presence is allowed.
• Organic particles. They contribute to the formation of silt, which impedes the water-carrying capacity of the concrete base.

The construction of the substrate is carried out according to the following algorithm:

To lay the pillow you need to dig a pit.

1. The soil under the pit is removed.
2. The bottom of the trench is filled with prepared sand.
3. The material is leveled over the pit, the uniformity of the backfill is controlled by the level.
4. The pillow is being compacted.

Crushed stone footing

To lay the material, a pit is prepared, 200-600 mm deep. If there is high groundwater in the area, the bottom is covered with film material. Laying begins with a backfill of coarse gravel, then fine gravel. This sequence will provide the foundation structure with constant drainage. This will increase the strength and rigidity of the substrate. The structure is covered with sand, which will ensure uniform transfer of the weight of the structure to the laid layers. This type of concrete footing is unreliable; it does not have a sufficient level of rigidity, which is why multi-storey buildings are not suitable for this purpose. Small-sized and outbuildings can be built on such a bedding.

The mechanism for arranging foundation preparation includes the following stages:

The stone cushion should be placed at the bottom of the pit.

1. The excavation is prepared and crushed stone is laid.
2. The material is leveled with shovels.
3. Crushed stone is compacted over the entire base area.
4. The hydraulic barrier is made from a bitumen mixture or film-roll material.

Such activities can be carried out on your own. If hired workers are involved, the required payment for the volume of work performed can be compared with the available information in EniR.

Design features of a slab monolith

What is the essence of a solid foundation slab? The fact is that it most evenly distributes the loads from the weight of the building over the surface of unstable soil. This is comparable to walking through snowdrifts: your feet sink, but if you wear skis or wide snowshoes, you can stay on the surface without any problems.

Definition of subsidence soil

Types of soils classified as subsidence

The house did not collapse only thanks to the slab foundation

There are several engineering solutions for such foundations, which we will discuss below.

Surface (floating)

The term “floating” is applied to a shallow slab on the grounds that during soil movements associated with heaving phenomena, it can change its spatial position, preserving the integrity of everything that rests on it. The slab can be solid, ribbed or lattice, assembled from intersecting precast reinforced concrete beams.

Unburied slab

A solid slab with low or zero depth (when only the fertile layer of soil is removed) is designed for soils that are most susceptible to subsidence and heaving, including bulk soils.

The greater the weight of the building, the less the soil underneath will deform. At the same time, the design of the slab base is monolithic, made of high-quality concrete, reinforced with profile rods with a diameter of at least 10 mm.

The top of the slab can also serve as a basement floor, but when a high base is needed, it can be provided either in a monolithic version (even at the stage of concreting the slab) or built from foundation blocks or bricks. Accordingly, the basement floor in this case will be installed separately, on top of this wall.

Slab with plinth wall (monolith)

Defining parameters

Professional design of the foundation (as well as the entire house) is not always available to individual developers due to the high cost of these services. Therefore, design parameters are most often taken approximately, taking into account only the “irreducible minimum”.

First of all, the question arises, what should be the thickness of the slab.

Table 1. Reinforcement options and base thickness

Fiberglass reinforcement is practically not inferior in characteristics to steel

1. The diameters of the reinforcement in the frame can be combined. In this case, large rods are placed closer to the base of the foundation, and smaller ones - in the upper row. Rods can be used not only steel, but also composite and fiberglass.
2. A shallow slab is usually poured flush with the soil surface. The depth of the pit consists of the total thickness of all layers - including: the sand-crushed stone underlying layer, which occupies the bulk of the volume of the pit; footings; waterproofing layers.
3. On average, the resulting cake is 65-75 cm thick. It is buried only if the project provides for a ground floor or basement. The height of its walls determines the level of the foundation.
4. The area of ​​the slab on each side should extend beyond the contours of the walls. The volume of concrete is calculated by multiplying its length, width and thickness. For the main filling, mixtures of class B20 are used, for the concrete base - B7.5.

Concrete strength class B20

Concrete preparation technology

The most expensive type of foundation substrate, but it is ideal for the strip or slab supporting foundation of the house. The concrete can be equipped with an additional metal reinforcing frame, which provides greater strength to the substrate. Before installing the structure, you should familiarize yourself with the technology, which includes the following conditions and steps:

The backing can be made without an armored belt, but then it should be a little thicker.

• Preparation of “lean” concrete. A solution of grades from M50 to M100 is used.
• Thickness of the structure. In the absence of high occurrence of soil water, it is 100 mm.
• Laying the auxiliary layer. A small layer of crushed stone or sand is placed at the bottom of the pit.
• Preparation power without an armored belt. If reinforcement is not installed, then the concrete substrate should have a thickness of 150-200 mm.
• Additional reinforcement. Metal rods with a diameter of 0.8 cm are used. The reinforcement bars are mounted in a vertical position with a headroom of 0.25–0.30 m above the concrete preparation surface.

Before installing the pit, the level of surface water on the building site is determined. This will be the “starting point” when constructing the footing - it should be higher. A trench is dug, the bottom of which is then compacted and leveled. To give the structure improved qualities, the bottom is covered with a thin layer of sand and gravel, which are leveled over the foundation pit. It is advisable to make a film or roll hydrobarrier to protect the monolith. Carefully install sections of reinforcement into the thickness of the base. It is recommended to fix the beacons at the level; they will make it easy to control the placement of the mortar. Next, the prepared concrete is poured. After its maturation, the surface of the concrete preparation is treated with bitumen mastic.

Plot for building a house

Before purchasing a plot, it is important to understand the scale of the future structure; it depends on the needs of the owners and their financial capabilities. On average, it is considered that one person needs 30 sq.m of living space for a comfortable stay

When choosing a site for construction, you need to pay attention to:

• distance from the city;
• infrastructure development - school, hospital, retail outlets;
• quality of roads;
• electricity;
• gas lines;
• environmental safety (absence of hazardous industries);
• soil type, freezing depth;
• title documents - cadastral number, compliance with the boundaries of the site.

When building a house, the first thing you will need is water. For this purpose, craftsmen are invited to point out the places where it is advisable to dig a well or tap a standpipe.

It is important to do this before construction work begins; perhaps there is an aquifer in the area where the house was planned. If you already have neighbors, you need to ask what kind of water is here and how deep the aquifers are located

Concrete preparation for the foundation

Soils have a heterogeneous structure. Under heavy loads they can shrink, sag and collapse. In order to evenly distribute the pressure from the building, reduce the settlement of the house and prevent further shrinkage deformations, various types of preparations are arranged under the foundations - sand, crushed stone, gravel or concrete.

In weak soils - peat bogs, sapropels, waterlogged clays or silty soils - this is not enough. In this case, the base is erected using concrete preparation for the foundation.

Why do you need a footing, in what cases is it made of concrete, and when can you get by with a cheaper option - sand or crushed stone preparation?

Functions of the footing

Concrete preparation for the foundation is a layer of lean concrete between crushed stone or gravel backfill and the material of the main structure. Its thickness is within 10 cm.

The main function of the footing is to provide reliable support for the foundation of the building:

• on weak soils;
• near slopes, embankments and slopes;
• at high compressive load from the structure;
• in earthquake-prone regions.

In these cases, the dimensions of the concrete are calculated according to the standards - SNiP 2.02.01-83, Construction Rules 50.101.2004, 63.13330.2012. They indicate the basic principles for selecting the composition of concrete, installing a preparatory layer, installing a reinforcement cage, and performing work.

Additional functions of concrete preparation are:

• ease of installation of prefabricated structures on a leveled surface;
• precise installation of reinforcement cages when constructing a monolith, since it is much more difficult to align them horizontally on a bed of crushed stone;
• in creating an additional protective layer from soil moisture that destroys the main structures;
• in the cost-effectiveness of using high-grade concrete when laying it on a leveled, dense base made of inexpensive material;
• By preventing the flow of cement laitance from the freshly poured mortar of the main foundation structure, the hydration of the binder grains is complete, and the grade of concrete is not lost.

It is advisable to arrange concrete preparation for massive and large-scale structures. Light frame or small buildings on flat terrain and dense soils are erected on a compacted base - sand and crushed stone bedding. Its purpose is to protect against freezing, remove soil moisture, and prevent soil heaving.

Regulatory and legislative framework

If you are going to build a strip foundation, then the GOST and SNIP data will definitely be useful to you:

• The basics of construction work on creating foundations from reinforced concrete slabs are recorded in GOST 13580-85;
• All standards for building foundations are summarized in Snip 2.02.01.83;
• The document on load-bearing and enclosing buildings is called Snip 3.03.01-87;
• All norms and requirements for the construction of foundations and other land buildings are included in Snip 3.02.01-87.

Types of preparation

The most common types of preparation:

• sandy;
• gravel or crushed stone;
• concrete;
• membrane

Sand and crushed stone preparation

At the first stage, after excavation work, backfill is made from inert materials, followed by compaction with tampers. The thickness of the sand, crushed stone or gravel cushion is 20-60 cm. If the groundwater level is high, geotextiles are spread along the bottom of the pit.

Large fractions are laid first, then medium ones. They provide drainage to the base. The top layer is covered with sand. This distribution of materials by size gives the cushion under a strip or slab foundation greater rigidity and strength. The use of sand in preparation is necessary for uniform transfer of vertical load to the underlying layers.

The requirements for fine aggregate are:

• they use sand with a grain size of 2-2.5 mm, the most suitable for filling pillows - crushed gravelly sand with low specific gravity and high water throughput;
• the amount of clay particles, lime and salt contaminants should be minimal;
• organic residues lead to a rapid loss of water permeability and siltation of the sand layer, so their presence is not allowed.

The backfill for the foundation is made of gravel, granite or crushed limestone with an average strength of M800 and a fraction size of 20-70 mm. Layer-by-layer compaction with a vibrating plate or manual tampers is mandatory every 50 mm. The sand is first spilled with water.

Concrete preparation

The cushion under the slab or foundation blocks is made in two ways. The first is pouring a layer of crushed stone with liquid bitumen, the second is installing a footing made of low-grade concrete M50-M100 with a layer of up to 10 cm.

A concrete pad for the foundation is made:

• pouring into a trench or the bottom of a pit without formwork;
• installation of formwork around the perimeter of the site and subsequent spreading of the concrete base;
• First, thin concrete is placed in the foundation form, then concrete of the design grade.

The solution is leveled using beacons or a rule, and compacted with a vibrator. The top of the concrete base is waterproofed with bitumen, rolled materials, and waterproof films.

Preparation with geomembrane

Polymer membranes have recently appeared on the construction market. Fiber is used to protect the foundation of a building from soil moisture, i.e. as waterproofing. What is fundamentally new is that the profile in the form of spikes simultaneously serves to strengthen the soil. Manufacturers claim that the use of geomembranes reduces the number of shrinkage cracks and redistributes forces when transferring load to the base. The cross-sectional shape prevents water from entering, and the voids between the insulation and the concrete are ventilated.

The fiber is laid using sand and crushed stone preparation; a layer of geotextile is first laid out. Membrane seams are connected by welding. The material is strong and durable, withstands high and low temperatures.

Cellular concrete - aerated concrete, foam concrete

Today this material is very popular in cottage construction due to its low cost, precise dimensions (blocks can differ only by ±2 cm), low thermal conductivity and low weight. Due to the precise geometric dimensions, blocks of cellular concrete are laid on a special glue, the layer of which is 2-3 mm, which is much thinner than the seam in brick construction. As a result, there is no cold bridge, which is the mortar joint between the bricks. Therefore, a wall made of cellular concrete has better thermal characteristics compared to a brick wall, and there is no condensation that forms on the cold bridge.

A type of cellular concrete is foam concrete, which, in addition to cement, water and sand, also includes a foaming agent. Foam concrete has a cellular structure due to the presence of closed pores throughout its entire volume. Such concrete is made in several ways; the finished material is foam blocks or a foam concrete mixture. The latter is manufactured on site and immediately poured into the formwork. Since the frame of the house consists of reinforced concrete pillars, foam concrete does not need to perform a load-bearing function. Therefore, such a material, with a density of about 250 kg/m³, is an excellent insulation material; in addition, the foam concrete layer is seamless, and there are no cold bridges in it.

In the process of choosing material for building a stone house, you should pay attention to the following parameters:

• the cost of loading, unloading and delivery;
• quantity and cost of the required masonry mortar;
• “shrinkage” parameters of the material - this affects the amount of cosmetic work after drying and shrinking the finished house.

When using aerated concrete blocks as a building material, it is necessary to strictly adhere to construction technology. In particular, you need to use special lintels for openings, U-blocks for reinforced belts and blocks for partitions between rooms.

You should familiarize yourself with the range of additional elements (quarters of door and window openings, reinforced belts, parts for making floors and lintels, etc.) in advance, since their production on site, often ill-considered, reduces the quality of the house.

Sequence of work

Work on installing a footing for a foundation made of lean concrete is carried out according to the following scheme:

1. Level the bottom of the pit or trench.
2. Large and medium crushed stone is poured, leveled, and compacted. Layer height - 10-15 cm.
3. The next step is backfilling the foundation with sand of fraction 2-2.5 mm, moistening, tamping.
4. Install the formwork under the cushion under the strip foundation.
5. Reinforcement mesh and vertical outlets are installed to connect the foundation with the preparation of the base.
6. To fill the cushion, use M100 concrete with Portland cement grade no lower than M500. Layer height - 10 cm.
7. The surface is leveled and tamped with vibrators to release air from the thickness of the solution.
8. After 3-7 days, the formwork panels are removed.

Before installing the foundation, you need to waterproof the pillow using coating or rolled protective materials. According to SNiP, permissible horizontal deviations should not exceed 5 mm when checking with a two-meter level, and along the entire length of the section - 20 mm.

Application of car tires

In order to build a small frame house, you can use simple car tires. It is necessary to lay a bandage beam on them. This material is the most accessible and cheap, and can last quite a long time. In order to equip the base for a frame house, you need to pour sand inside the tires about 3/4 of the height. From time to time it will need to be watered and compacted.

After this, fill the tires to the brim with crushed stone. As a result of the work carried out, you will receive a good alternative to a conventional foundation. Here's how to make a house without a foundation - just put a few tires on it. The base has the following advantages:

1. The foundation has very good shock-absorbing qualities. You can protect your entire house from seasonal swelling of the soil.
2. By erecting such a foundation, you will not violate the overall environmental friendliness of the entire building.
3. On what basis will you get a very stable structure. Judging by the reviews of people who chose just such a foundation for construction, we can conclude that there are no wall distortions at all, and door and window openings are also stable.
4. The cost of building such a base is very low; tires can be found for free at any tire shop.
5. Installation is very simple, as is the device, so this base has earned popularity among builders.

Such a foundation shows itself very well in the construction of a sauna or bathhouse, outbuildings, gazebos, and other buildings.